Piano construction



Jan. 5, 1943.

G`. w DEMUTH PIANO CONSTRUCTION Filed Oct. 26, 1938 IIIHHIllHlllIHlllllllllllllllllHll l'lllllllllll attorneg Patented Jan. 5,' 1943 I PIANO CON STRUCTION Galan W. Demuth, Westville, N. J., assignor to Radio Corporation ot America, a corporation of Delaware Application October 26, 1938, Serial No. %7,001

3 Claims.

This invention relates to piano construction` and more particularly to the Construction of electrical pianos wherein the vibration of the strings is translated into acoustic vibrations electrically instead of mechanically.

In mechanical pianos, strings pass from pins attached to the frame over a bridge and thence to the tuning pins at the opposite ends of the string. The bridge rests upon a soundboard and the mechanical vibrations of the string are communicated to the bridge and to the soundboard which in turn communicates these vibrations to the air. When the bridge vibrates with the strings, it tends to communicate the vibrations to adjacent strings, which are thereby forced into vibration and the vibrations of these adjacent strings are likewise imparted to the soundboard, thereby affecting the tone quality of the piano. At the time a note is sounded the damper of that note is raised while the other strings remain damped with the exception of the highest octave which is' usually not provided with dampers. The

vibrations of these other strings are accordingly rapidly damped out both by the dampers and by the transmission of the acoustic energy from the soundboard.

In the heretofore attempted manufacture of electrical pianos, while it has been the impression of the makers that the structure of the mechanical piano should be copied as nearly as possible and although the use of electric pickups from the strings, and electromagnetic amplifier and loud speakers have made elimination of the soundboard possible, nevertheless the bridge construction and operation customary in the mechanical pianos has been adhered to, this copying even going so far as to provision of means whereby the bridge could vibrate in the identical manner in which it vibrated in a mechanical piano.

I have discovered that in an electric piano the aforesaid copying of construction and operation of a mechanical piano is not only undesirable but is definitely detrimental and I have accordingly devised a construction which avoids the detrimental efiects thereof..

One advantage of an electrical piano having electromagnetic or electrostatic pickup from the vibrations of the strings lies in the fact that the power absorbed from the string by the pickup is extremely small and a note can accordingly be sustained for a longer time than in the case of a mechanical piano where the vibration of the string is used to drive a soundboard. I have discovered that if the vibration of the string is used ing of the string is produced which tends to decrease the time during which a note may be sustained and to increase the rate at which the loudness of the new note falls off. In order to avoid this difllculty, I mount the piano bridge rigidly to the frame, thereby preventing vibration of th bridge and at the same time materially decreasing the damping eifect upon the string. I thereby sustain the note which is sounded at a more uniform amplitude and for a longer time than is otherwise the case. I find no disadvantage from the effect of this arrangement on the tone quality of the piano as the decrease in clamping of the tone which is struck corresponds to the decrease in clamping of the remaining strings and these other strings are accordingly driven in a proper amount through the atmospheric acoustic coupling to the sounded strings thereby providing substantially the same tone quality as would be produced in a standard piano.

A further advantage of my Construction is that the relatively more rigid position of the strings prevents the piano from getting out of tune as rapidly as would be the case with a non-rigid bridge.

One object of my invention is to provide an improved construction for a piano.

Another object of my invention is to provide a piano Construction in which the vibration of the strings is damped less rapidly than is customary.

Another object of my invention is to provide a piano Construction in which coupling between v the strings is accomplished substantially atmospherically.

Another object of my invention is to provide a piano which will stay in tune longer than has* heretofore been the case.

Another object of my invention is to provide a more substantial piano Construction.

Other and incidental objects of my invention will be apparent to those skilled in the art from a reading of the following specification and inspection of the accompanying drawing in which Figure 1 is a front view of a preferred form of the invention;

Figure 2 shows a section of the line 2--2 of Figure 1;

Figure 3 shows a simplified form of the invention; and

Figure 4 is a section taken longitudinally of the I member 32 in Figure 3.

The simplified form of the invention shown in to drive a vibratable bridge, a considerable damp- 55 Figs. 3 and 4 will be first described.

board is omitted, as it is entirely unnecessary.

The bridges `l6 and |8 are accordingly supported in accordance with my invention by means of the bars 3I, 32, 33 and 34. These bars are made of an appropriate rigid strong material such, for example, as cold rolled steel and each of these bars may be, for example,- a half-inch thick by an inch and a half' wide. The bars are secured to the string plate by appropriate bolts 35 and the bridges IS and I 8 are Secured to the bars by means of appropriate wood screws 36. Although this portion of the piano construction is shown without any strings, the strings will, as usually, be affixed to the string plates I 4 and !5. It will be apparent from an inspection of Figs. 3 and 4 that 20 the bridges Hi and l8 will be rigidly fixed in relation to the piano string plate and that the rigidity of their supporting bars will be so great in relation to the force of vibration of the strings that practically no movement of the bridges will occur.

Referring now to the preferred form of the invention as shown in Figs. 1 and 2, the piano is provided with the usual casing ID 'and keyboard ii and with a frame which, in these figures is indicated at l2. The usual strings |3 are provided which are, as is customary, attached to pins in the string plates !4 and !5. In the bass section the strings pass over the bridge |6 and over a group of electromagnetic or other electrical pickups generally indicated at I'I. Thesepickups are preferably constructed as described and claimed in my application Serial No. 232,526, filed September 30,- 1938. In the treble section the strings pass over the bridge !8 and the series of pickups generally u indiatedat IS.

In this form oi' the invention, the bridges I 6 and |8 are mounted in appropriate recesses in the string plates M and IS so that the bridges are supported directly upon these string plates, which form a portion of the string plate of the piano being cast integral therewith. The bridges may be cemented to the string plates and, in addition, are sefured thereto by appropriate wood screws 40 and 4 It will be apparent to those skilled in the art that in this construction the bridges are even more rigidly secured to the string plate than in the simpler construction shown in Figs. 3 and 4. The two forms of the in'vention are substantiaily identlcal in operation since in either case the bridges are rigidly connected to the frame.

It will be apparent to those skilled in the art that groups of pickups i'l and !9 may be connected in any known manner to an appropriate thermionic amplifier and the amplifler'connectedto an appropriate sound reproducer or londspeaker. v

Having now described myinvention, I claim:

1. In a soundboardless piano, a substantially fiat rigid separately formed metal string plate, a separately formed bridge on said plate, removable means for iastening the bridge in place, strings all fastened at both ends to said plate and resting on the free or exposed edge of said bridge, the base of the bridge being rigid with the plate, so that the bridge is vibrationless and entirely between the plate and the strings, and Whereby said plate and bridge form a structural unit, means to solidly support the plate, and 'means for fastening the plate in place,'whereby.-.the strings and bridge are supported entirely by "the plate.

2. In a piano, a separately formed metal string plate formed in one rigid section, having a seat formed along an edge thereof, on the face of the plate, a more or less curved and separately formed bridge disposed on said seat, the latter conforming`to the shape 'and curvature of the bridge, fastening means extending through the plate from the back thereof to secure said bridge solidly in position, and strings engaging said bridge and anchored at both ends on the face of the plate.

3. A structure as' specified in claim 2, said bridge being formedof non-metallic material, and said fastening means comprising screws inserted through the plate and screwed a distance into the bridge.

GALAN W. DEMUTH. 

